For writting "F0.1" or "i0" is allowed, for reading not.
g95 gives: Warning: Positive width required in format string NAG f95: Error: Zero field width for F edit descriptor invalid for input -- Summary: edit descriptor checking: Compile-time check for zero width for reading Product: gcc Version: 4.3.0 Status: UNCONFIRMED Keywords: diagnostic Severity: normal Priority: P3 Component: fortran AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: burnus at gcc dot gnu dot org http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32483